1. Technical Field of the Invention
The present invention relates to a plasma processing apparatus utilizing a microwave.
2. Description of the Related Art
Conventionally, there is known a plasma processing apparatus which includes a plane antenna, as shown in FIG. 3.
This plasma processing apparatus 71 has a processing container 73 in the form of a bottomed pipe as a whole and a quartz plate 75 arranged on a ceiling part of the container 73 in an airtight manner, forming a closed processing space S inside the container 73. Accommodated in the processing container 73 is a mount table 77 which mounts a semiconductor wafer W thereon. The mount table 77 is connected with a bias high-frequency power source 79 through power lines. Through the sidewall of the container 73, a gas nozzle 81 is arranged to introduce process gas into the container 73 and further connected with a process gas source 83. Further, the container 73 is provided, in a bottom thereof, with exhaust ports 85 communicated with a not-shown vacuum pump.
While, a plane antenna member 87 is arranged on the quartz plate 75 closing up the top part of the processing container 73. The plane antenna member 87 is formed by a bottom plate of a radial waveguide box 89 and also attached to the top of the quartz plate 75. The radial waveguide box 89 is provided as a short, disc, hollow and cylindrical container. Connected with the top center of the disc radial waveguide box 89 is an outer tube 93A of a coaxial waveguide 93 which has the other end connected with a microwave generator 91. In the coaxial waveguide 93, an inner cable 93B is connected to the center of the disc-shaped antenna member 87.
The antenna member 87 is made from a copper plate and has a number of slots 95 formed therein. In order to shorten a wavelength of microwave thereby realizing a short guide-wavelength, the radial waveguide 89 fills its interior with a dielectric 97 of a predetermined dielectric constant.
In the constitution mentioned above, the microwave produced in the microwave generator 91 is propagated in the coaxial waveguide 93 and expands in the radial waveguide box 89 in the radial direction. Then, the microwave is emitted through the slots 95 of the antenna member 87 downwardly thereby to produce a plasma in the processing container 73.
In the above processing apparatus 71, however, an uneven electric field is formed below the plane antenna member 87, causing an unevenness in the processing for the wafer W. That is, the electric field emitted through the slots 95 of the antenna member 87 is reflected on the inside wall of the processing container 73 to intensify the electric field at the center of the container 73, as shown in a lower part of FIG. 3. Therefore, a problem arises in that an unevenness is produced in processing the wafers, particularly, large-diameter wafers.
In order to solve the above-mentioned problem, the object of the present invention is to provide a plasma processing apparatus which is capable of realizing a generally uniform electric field below the antenna member to accomplish an uniform wafer processing.
The first feature of the present invention resides in the provision of a plasma processing apparatus comprising: a processing container shaped to be a hollow cylinder with a bottom and also provided, inside thereof, with a mount table for mounting an object to be processed thereon; a lid body for covering an upper opening of the processing container in an airtight manner, the lid body having a dielectric; a microwave supplier for supplying a microwave; a waveguide having one end thereof connected to the microwave supplier, the waveguide extending from the microwave supplier toward the lid body and also having an waveguide space formed therein; a radial waveguide box connected to the other end of the waveguide, the radial waveguide box having a flange part expanding from the outer end of the waveguide outward in the radial direction and a sidewall extending from the flange part toward the lid body downward thereby to define a waveguide space therein; an antenna member for covering a lower opening of the radial waveguide box and having a plurality of slots formed therein, the antenna member being arranged in parallel with the lid body; and a metallic reflector formed at the center of the antenna member on the side of the mount table so as to extend toward the mount table, for reflecting a high-frequency electric field reflected by an inner wall of the processing container.
According to the second feature of the invention, the reflector is arranged to project from the lid body into the processing container.
According to the third feature of the invention, the reflector is arranged not to project from the lid body into the processing container.
According to the fourth feature of the invention, a tip of the reflector is embedded in the lid body.
According to the fifth feature of the invention, the reflector is shaped in a hollow cylinder or a pillar.
According to the sixth feature of the invention, the reflector is shaped in a hollow cylinder with circular sectional shape or a pillar with circular sectional shape.
According to the seventh feature of the invention, the reflector is shaped in a hollow cylinder with polygonal sectional shape or a pillar with polygonal sectional shape.
According to the eighth feature of the invention, in the plasma processing apparatus, an absorbing member is arranged close to the outer circumference of the radial waveguide box to absorb the high-frequency electric field.
According to the ninth feature of the invention, in the plasma processing apparatus, an absorbing member is arranged in the outer circumference of a space between a lower face of the antenna member and a lower face of the lid body having the dielectric.
According to the tenth feature of the invention, the waveguide includes an inner conductor and an outer conductor in coaxial with the inner conductor so that the microwave is propagated between the inner conductor and the outer conductor, an end of the outer conductor on the side of the lid body being connected with the radial waveguide, while an end of the inner conductor on the side of the lid body being connected with a central part of the antenna member.
According to the eleventh feature of the invention, the waveguide has circular sectional shape, microwave in TM mode being propagated therethrough.
The twelfth feature of the invention resides in the provision of another plasma processing apparatus comprising: a processing container shaped to be a hollow cylinder with a bottom and also provided, inside thereof, with a mount table for mounting an object to be processed thereon; a lid body for covering an upper opening of the processing container in an airtight manner, the lid body having a dielectric; a microwave supplier for supplying a microwave; a waveguide having one end thereof connected to the microwave supplier, the waveguide extending from the microwave supplier toward the lid body and also having an waveguide space formed therein; a radial waveguide box connected to the other end of the waveguide, the radial waveguide box having a flange part expanding from the other end of the waveguide outward in the radial direction and a sidewall extending from the flange part toward the lid body downward thereby to define an waveguide space therein; an antenna member for covering a lower opening of the radial waveguide box and having a plurality of slots formed therein, the antenna member being arranged in parallel with the lid body; and an absorber arranged at the central part of the antenna member on the side of the mount table so as to project toward the mount table, for absorbing the high-frequency electric field.
According to the thirteenth feature of the invention, in the above plasma processing apparatus, the absorber is arranged to project from the lid body into the processing container.
According to the fourteenth feature of the invention, the absorber is arranged not to project from the lid body into the processing container.
According to the fifteenth feature of the invention, a tip of the absorber is embedded in the lid body.
According to the sixteenth feature of the invention, the absorber is shaped in a hollow cylinder or a pillar.
According to the seventeenth feature of the invention, the absorber is shaped in a hollow cylinder with circular sectional shape or a pillar with circular sectional shape.
According to the eighteenth feature of the invention, the absorber is shaped in a hollow cylinder with polygonal sectional shape or a pillar with polygonal sectional shape.
According to the nineteenth feature of the invention, in the plasma processing apparatus, an absorbing member is arranged close to the outer circumference of the radial waveguide box to absorb the high-frequency electric field.
According to the twentieth feature of the invention, in the plasma processing apparatus, an absorbing member is arranged in the outer circumference of a space between a lower face of the antenna member and a lower face of the lid body having the dielectric.
According to the twenty-first feature of the invention, the waveguide includes an inner conductor and an outer conductor in coaxial with the inner conductor so that the microwave is propagated between the inner conductor and the outer conductor, an end of the outer conductor on the side of the lid body being connected with the radial waveguide, while an end of the inner conductor on the side of the lid body being connected with a central part of the antenna member.
According to the twenty-second feature of the invention, the waveguide has circular sectional shape, microwave in TM mode being propagated therethrough.
The above and other features and advantages of this invention will become apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing preferred embodiments of the invention.